The present invention relates, generally, to a balloon catheter for use in the region of vessel branchings and, in particular, in coronary vessels. More specifically, the present invention relates to a catheter comprising a catheter stem, at the distal end of which are provided at least one balloon and at least one first guide means which is arranged in the region of the balloon for positioning the balloon in the region of a vessel branching, wherein the first guide means is adapted to be introduced into the lateral branch of the vessel transversely with respect to the longitudinal direction of the balloon catheter.
Balloon catheters are used for dilating constricted vessels in the human and animal body. The balloon, which is typically arranged at the distal end of the catheter stem, is generally introduced into the vessel system at a distance from the constriction and moved within the vessel system to the position of the constriction. The balloon is then expanded to enlarge the constriction by the action of pressure. Frequently, a tubular intraluminal support element, referred to as a stent, is arranged on the balloon such that it can be radially stretched and deformed upon expansion of the balloon. When the balloon is removed from the vessel, the stent remains in its radially deformed condition in the vessel thereby supporting the vessel in a permanently expanded state.
In a region containing vessel branchings and, in particular, for coronary vessels, it is necessary, particularly when a stent is to be implanted, for the balloon to be positioned as accurately as possible with respect to the vessel branching. For that purpose, a first guide means is typically provided, which is arranged in the region of the balloon and which, for the purposes of positioning the balloon in the region of a vessel branching, can be introduced into the lateral branch of the vessel transversely with respect to the longitudinal direction of the balloon catheter, thus serving as a positioning aid.
Such a balloon catheter is known in the prior art, such as, for example, from European patent application EP 0 904 745 A2, in which a guide wire which can be introduced into the lateral branch of the vessel is arranged along the outside of the balloon. This conventional balloon catheter design, however, suffers from the disadvantage that, upon expansion of the balloon, the guide wire, which is arranged on the outside of the balloon and which is surrounded by a guide tube, causes an irregular load to be applied to the vessel or the stent, if such is provided, in a peripheral direction. This irregular load is the result of the outwardly bulged configuration of the balloon in the region of the guide wire. The outwardly bulged configuration results in unwanted irregular deformation of the wall vessel or of the stent, which is disposed between the balloon and the wall of the vessel, in the peripheral direction. In this irregular deformed situation, relatively small radii of curvature, that is to say a relatively high degree of deformation, is induced in the region of the guide wire. This deformation can have a detrimental effect, not only on the weakened wall of the vessel, but also on the filigree structure of a stent. The stent structure may even suffer from local ruptures, which must be avoided.
A further disadvantage of the known balloon catheter lies in the relatively large transverse dimension of a balloon with a guide wire and a guide tube disposed on its outside surface.
Accordingly, there is a need for a balloon catheter which both provides the smallest possible transverse dimension for the balloon, and also ensures that the elements disposed therearound are deformed as uniformly as possible in the peripheral direction of the balloon upon expansion.
In accordance with the invention, a balloon catheter is provided for use in the region of vessel branchings and, in particular, of the coronary vessels. The balloon catheter of the present invention is designed to provide a uniform deformation of adjoining elements in the peripheral direction of the catheter upon expansion of the balloon. In one embodiment of the invention, the balloon catheter comprises a catheter stem, at the distal end of which are provided at least one balloon and at least one first guide means arranged in the region of the at least one balloon for positioning the balloon in the region of a vessel branching. In this embodiment the first guide means is adapted such that it may be introduced into a lateral branch of the vessel by extending the first guide means transversely with respect to the longitudinal direction of the balloon catheter.
Although the above embodiment is described in terms of a single balloon, it should be understood that the term balloon is used herein in a broad sense and is also intended to embrace any suitable arrangement of individually inflatable chambers. For example, in one embodiment of the present invention, the balloon has at least two inflatable chambers which are longitudinally spaced from each other along the length of the balloon catheter. In this embodiment the first guide means is arranged between the two chambers such that the outside of the balloon is not deformed by the presence of the first guide means. During operation of this embodiment, the substantially circular-cylindrical balloon is able to exert a substantially uniform deformation force and produce substantially uniform deformation in the peripheral direction.
In an alternative embodiment the balloon in accordance with the invention has at least two chambers which are longitudinally spaced from each other along the length of the balloon catheter. In this embodiment the first guide means can be arranged between the two chambers such that any guidance or feed means, such as, for example, a guide wire having a guide tube or hoze can be integrated into the stem of the catheter thereby allowing for a balloon catheter having a smaller transverse dimension.
As will be understood, the first guide means can take any form suitable for assisting with positioning of the balloon catheter into a lateral branch of a vessel, such as, for example, as a balloon which would extend into the lateral branch of the vessel upon expansion. In one alternative embodiment, the first guide means comprises a first guide wire. The first guide wire may be guided by any suitable means. In one embodiment of the invention the first guide wire is controlled through a mechanism in the catheter stem. In this embodiment a lateral exit for the guide wire would be provided in the catheter stem between the two inflatable chambers.
In another alternative embodiment of the invention a second guide wire is provided for guiding the balloon catheter in a longitudinal direction. In this embodiment the second guide wire can also be guided by a mechanism within the catheter stem, in which case the catheter stem is provided with a second guide wire exit means at its distal end.
In yet another alternative embodiment one or both of the guide wires can be provided with X-ray markers, such as, for example, an X-ray-opaque coating or the like in order to make it easier to monitor the positioning operation.
In still another preferred embodiment of the balloon catheter according to the invention, the first guide means is also adapted to deform support elements of a stent arranged in the region of a vessel branching such that the passage between the two vessel branches is opened.
In still yet another preferred embodiment of the balloon catheter according to the invention, the inflatable chambers are adapted to be filled separately.
In still yet another embodiment, the invention concerns a system for dilating constricted vessels and, in particular, coronary vessels, in the region of vessel branchings. The system comprising a balloon catheter according to the invention and a stent arranged on the balloon thereof. In this embodiment, the stent is provided with at least one branching portion arranged at the periphery of the peripheral casing of the stent in the region adjoining the first guide means. Also in this embodiment the branching portion of the stent may include at least one first support element which is provided for supporting the vessel transition in the region of a vessel branching and which can be pivoted substantially radially out of the peripheral surface and the first guide means is further adapted to pivot the support element of the peripheral surface. This provides a system for dilating constricted vessels, in the region of vessel branchings ensuring reliable dilation of the vessel including support for the transition into the branching-off branch of the vessel.